This is our 155 mil Door pack (10 pieces - 5" x 8.25") (~2.8 sq ft)
 
Vibraflex is a Bitumen plastic material that is used for dampening vehicles and other metal enclosures.  The advantage of vibraflex vs traditional Butyl sound dampeners is that after it is applied it retains it shape as a thermal formed sheet.  When tempuratures are within normal ranges this stuff is as hard as a rock! If the tempuratures are high VibraFlex reacts EXACTLY the same as traditional dampeners as a mass loader!
 
1.7 LBS per sq ft